(Murray Middleton is an award-winning short-story writer and AFL fan.)

In the past 18 AFL seasons there have been 47 rule changes.  The most contentious change in recent years has been the ‘substitute rule', which was ratified in October 2010.  Collingwood coach Mick Malthouse - one of the best exponents of rotations - remains a critic of the rule, as is his former assistant, Brad Scott.  Essendon captain Jobe Watson was so incensed by the change that he toyed with the notion of staging a player-sanctioned protest prior to his side's round one clash with the Western Bulldogs.

Despite the heavy criticism of the substitute rule, the lime green vest is likely to remain in the game for many seasons to come.

It is the halfway mark of the home-and-away season.  The jury is still out on the substitute rule.  At first glance, it appears to be operating more smoothly than the revised advantage rule.  It will take time for coaches and players to learn how to contend with, and exploit, the new rule.  The most controversial moment to date occurred in round two when Richmond spearhead Jack Riewoldt was substituted due to concussion.  Riewoldt directed his anger, albeit rather theatrically, at his own club's interchange stewards.  For players with an appetite for the contest, the finality of donning the red vest can be hard to take.

There have been a number of different approaches to the new rule.  In round one, Sydney named ruckman Mark Seaby as a substitute against Melbourne.  John Longmire held Seaby back until halfway through the final quarter.  He had little impact and was dropped the next week.  In round two, St Kilda took the baffling measure of naming its No.1 tagger, Clinton Jones, as its substitute.  In round nine, Collingwood employed Alan Didak as a ‘super sub', which revived memories of Sir Alex Ferguson bringing Ole Gunnar Solskjaer off the bench for Manchester United in the late 90's.

The most memorable substitute performance of the season came from Sydney's red-headed youngster, Gary Rohan, against the West Coast Eagles in round three.  When Rohan replaced Sam Reid halfway through the third quarter, his side was trailing by three goals.  He injected some much-needed zip into the Swans' line-up.  Rohan ran the lines, gathered nine possessions and kicked a crucial goal in the last quarter. He moved with the voracity and fearlessness of youth.  The Swans prevailed by 13 points.

Another notable performance came from Hawthorn's Jordan Lewis in round two.  Lewis was activated five minutes into the third quarter when Brent Renouf was concussed.  Owing to its deplorable kicking, the Hawks were trailing Melbourne by 19 points.  Lewis added some grunt to the midfield and, most importantly, enabled Shaun Burgoyne to drift forward.  Hawthorn kicked 8.11 in the third quarter to blow the Demons out of the water.  Burgoyne kicked four goals and Lewis collected thirteen disposals in less than a half of football.

In round two, Andrew Krakouer proved to be the icing on the cake when Collingwood defeated North Melbourne by 87 points.  Krakouer gathered 12 possessions and chimed in with a clever goal.  Sydney's Lewis Jetta also played a crucial quarter of football in the Swans' one-point triumph over North Melbourne in round 10.  At one stage in the last quarter, he embarked upon a daring run along the boundary line which resulted in an Adam Goodes goal.  Although Jetta only collected five disposals, he made them count.

Several clubs have employed young players as specialist substitutes in the hope of easing them into the pace of the game.  In four of the first five rounds, West Coast used its No.4 selection in the national draft, Andrew Gaff, as a substitute. Geelong's Allen Christensen started four of his first five games wearing the green vest.  His most notable performance came in the Cats' upset victory over Collingwood in round eight.  St Kilda recently used Jamie Cripps off the bench as a small forward.  Cripps kicked six goals in three games as a substitute before his season was prematurely ended by injury.

The new rule has also placed more emphasis on the output of the ruckman come utility; a role pioneered by Leigh Brown last season.  The most successful convert to this role - until his season-ending Achilles injury at the weekend, anyway - was Hawthorn's Jarryd Roughead.  Roughead had been asked to spend lengthy periods in the ruck since David Hale got injured in round eight. He offered the Hawks an athletic target around the ground who was capable of taking contested marks and competing well at ground level. Instead of resting on the interchange bench, Roughead was able to rest up forward. Conversely, the days of the dinosaur (Mark Blake, for instance), appear to be numbered.

It is difficult to know how to appraise the game of a substitute, particularly with regard to selection the following week.  The flaw in adopting a perennial substitute is that the player will inevitably lose match fitness.  This can be a problem if they are required to come on early in the case of injury.  Most clubs seem loathe to activate their substitute prior to the halfway mark of the third quarter, for fear of being left with limited rotations.  It can also be difficult for a player to enter a match not knowing when, or if, their opportunity will arise.  There is little doubt that being a substitute is one of the toughest assignments in football.

The prototype for the substitute is yet to be finalised.  Clubs have a further 12 rounds to experiment before settling on an approach which must withstand the rigours of finals football.  At present, speed is essential.  Flexibility is a must.  Grunt is a bonus.  Youth, in its precociousness, can go either way.  It will be interesting to see how the substitute rule is utilised by the respective teams on Grand Final day.  As Ted Hopkins demonstrated in the 1970 Grand Final, sometimes the balance of a match can rest in the lime green vest.